I was lucky enough to be given an Eheim external thermofilter by a friend who was moving and could no longer have fish at his new place.
Although they don't do the particular model I have anymore I find it brilliant, it keeps the water at the right temp and only needs cleaning once every couple of months and it does an excellent job with the water, filtering out all the "crap" and keeping my fish happy.
They are quite pricey and I am not sure if I would have bought one when I first started because of that, but having used this for the last six months I would not use anything else.
Please bear in mind though it will not be worthwhile buying one of these if you only have a small tank, so I would suggest a little research as I have found the advice given in your lfs is not always the best.
Hope this helps and if you need any other advice just let me know.