SFF, I personally find them to be easier than Bettas - possibly because this year I've lost so many Bettas due to water, disease, etc - but the axies are fine. Not sure... maybe that's it. Bettas are a lot harder than the LFS makes it look!
As for their activeness - youngsters swim around a lot, but as they become adults, they tend to stay at the bottom a bit more. They generally laze around the tank-bottom, but do swim sometimes. I'm leaning towards them being partly nocturnal, as I'm pretty sure they have their swim parties at night time when I'm not looking! As for them looking still at the LFS - yes they generally are still, but the LFS don't really look that happy, as do the bettas in jars. They are often housed on gravel in LFS, and anything smaller than the size of their head is eaten, and gravel can impact them.
Axolotls prefer a gentle current. Strong currents stress them out. I have a canister filter with a spray bar, that seems to be OK.
As for a chiller - very much recommended! I could REALLY use one of them, Summers are a NIGHTMARE! I just can't seem to keep it cool easily at all.
I recommend reading these links, if you haven't seen them already -
http://www.axolotl.org/index.htm
http://www.caudata.org/cc/articles/articles_axolotl.shtml
http://all-about-axolotls.blogspot.com/
Feel free to ask any questions you may have. :)