I've never served but I've worked closely (on the government side, private consulting side, and just an ordinary citizen side) with a number of different city commissions. Some are very political (like Planning commission), others less so. To a certain extent, there's the chance that you'll fall under political pressure on any commission ("if you want to be re-appointed next term, it would be nice if you could vote this one down please, k thx").
I've given some thought to serving on a less political commission, but not ready to devote the time to it yet. I try to stay involved with master planning for schools, parks, etc. and give feedback to the policymakers.
Retired in 2013 at age 33. Keeping busy reading, blogging, relaxing, gaming, and enjoying the outdoors with my wife and 3 kids (4, 10, and 11).