What's it about?
Setting: Mediaeval stylefantasy land
When he tries to save a girl he thinks is about to be hit by a truck, Kazuma Sato ends up in limbo, where goddess Aqua gives him a choice: move on to heaven, be reincarnated on Earth or go in his current body with his memories and abilities intact to an RPG style fantasy land. That land is in crisis, and Kazuma could be a hero in their fight against the Devil King.
When told he can take one thing with him, maybe a skill or a weapon, Kazuma chooses Aqua herself... only to regret it as soon as they reach the new world. Now he is stuck with an devastated goddess with below average intelligence and no combat skills, who can't leave until the Devil King is defeated.
How's the fanservice content?
First fanservice: 1 minute 29 seconds in, when we meet Aqua. Well, Aqua's butt. I think whoever draw this was expressing their unhappiness with their job through the medium of weird proportions.
Fanservice Assessment rating: Obvious. I gave it the benefit of the doubt in the pilot, and episode 2 actually erred towards Low, but then episode 3 happened and suddenly Kazuma has the ability to magically steal underwear from the women around him.
For a moment we think Kazuma might face some consequences for this, as one of the party loudly tells the rest of the group about his panty blackmail in front of a room full of (theoretically) strong women...
What actually happens is that a masochistic female knight admires the "savagery" of this act so much she begs to join his party so she can be treated just as abominably. Kazuma has already deemed her too useless and weird for his party (while acknowledging how hot she is) but since she's been asking to join his party for most of the episode it's not exactly a specific consequence for his actions here.
Speaking of the knight, she proves her worth by the end of the episode - by allowing herself to be hit by flying cabbages, mostly in the chest.
What's good about it?
At its best, Konosuba can be summed up as "Unsympathetic, ineffective people band together to make it through a fantasy land that doesn't follow RPG rules." Requiring Kazuma to work his way up to an RPG bare minimum level of skill and equipment via the most unglamorous tasks imaginable is perfect, and the funniest moments come from characters puffing themselves up with ego and being deflated by reality. It's a solid premise which I expect a lot of people to enjoy.
The other members of Kazuma and Aqua's party, explosive arch wizard Megumin and masochistic crusader Darkness, are a lot of fun to watch. Kazuma's desperate attempts to politely get out of forming a party with either of them plus Megumin's pompous introduction are the highlights of the series for me so far. His internal monologue gets a lot funnier once they're in the picture.
I won't be watching any more of Konosuba because I can't stand Kazuma. He's entitled, selfish, rude and malicious, and that makes for a pretty unpleasant main character. This can work brilliantly in a comedy as long as he faces consequences for his awfulness (I refer you to It's Always Sunny in Philadelphia), but he doesn't often face direct consequences for his behaviour while the female characters do.
In the pilot they make a point of Aqua saying what a capable and reliable guy he is, despite being called what translates as a "fucking bitch" for mentioning that Kazuma is a shut-in NEET (Not in Education, Employment or Training, an accurate statement by Kazuma's own admission). Aqua accepts Kazuma's insults and rudeness without a word and even comes to respect him, despite the fact that she's apparently used to being worshipped? It doesn't make sense.
By episode 2 Aqua and Kazuma are being terrible to each other and suffering for it accordingly, which is a lot easier to watch, but she's still more supportive of him than he deserves. Why would she even stay with him? Her stats are among the highest while Kazuma's are the lowest; why not go attach herself to some warrior party with a good chance of defeating the Devil King quickly so she can go home?
The easy fix for this would have been to keep Aqua consistently terrible from her introduction. She's pretty awful when we first meet her, making fun of the way Kazuma died and casually eating crisps while he chooses his fate. She is devastated when she arrives in the new land with Kazuma; instead of this, make her furious with Kazuma, and too used to being waited on to adjust to everyday life in the real world. They could be determined to split up as soon as they've had their skills assessed at the guild, then change their mind when their stats come back. Aqua could realise Kazuma's the only one who won't make her pull her weight in the team, while Kazuma could realise Aqua's stats would make his party more appealing for other people to join. They would be in a reluctant partnership, each trying to get the most out of the other and looking for the first opportunity to ditch them.
Instead though, Kazuma is shown as the straight man surrounded by wacky women he doesn't like or respect. Again, that can work as long as the feeling and treatment are mutual, but it's lopsided in Kazuma's favour. The premise is great, but this execution makes it hard for me to enjoy. Once I hit the point where a young girl was crying because her underwear was stolen from her body and a woman was having an orgasmic response to being hit by sentient vegetables, I felt pretty comfortable walking away from this series.