The vast majority of user reviews and most official reviews have been excellent. A small number of them have said the game is too slow.
Eufloria was designed to be slow and relaxed to play so this is a matter of taste!
However, you can play Eufloria very fast, as I do, by employing tactics which don't involve stockpiling huge numbers of seedlings. Stockpiling is a perfectly reasonable way to do it, but it takes longer and it can also result in an overworked iPad (especially the iPad 1). Making your moves quickly and definitively is a really fun way to play, and there are some other interesting tactics you can use too
I can beat almost all the levels in under 10-15 minutes real time, if not less.