I've been playing the game for a couple of months now (they had a soft-launch in Finland, quite naturally as the company is Finnish).
I really like the game, but I cannot compare it to others in the same genre since I haven't really been playing other modern mobile games that much. The game is in general well balanced and the developers monitor the game closely. Small tweaks are released every few weeks to fix cards that are either too powerful/weak or simply being used too much/little, and these are communicated in advance with clear motivations and they have never made any strategy obsolute in one change. The developers are in general skilled and they have, for example, the main developer of Eclipse in the company but I haven't asked whether he is working on this game or not. In other words, I believe the game is designed so that boardgamers should like it.
The natural issue with this sort of games is the role of real-world money. It is perfectly possible to play without paying them anything and be fairly competitive (I can comfortably play at the highest arena and I haven't spent anything on the game), but reaching the top of the global leaderboard is most likely out of the question. The playing ground for the absolute top is levelled by tournament rules that gap the cards to reasonable levels (levels that you can be reached in perhaps 3-5 months of active playing; the company claims 2-3 months but that is not true for the epic cards) once you are high enough in the ranking, but unfortunately it is becoming near impossible to reach that ranking without paying something -- and once you start paying you would need to go to hundreds (if not thousands) of euros to actually have a big impact. Apparently some (mostly Asian) players have been paying thousands or even tens of thousands for decks with max-level cards; reaching those levels by playing would take probably tens of years assuming the servers existed that long... Yep, Supercell really knows how to make money with this kind of games.
So, I do recommend the game but suggest accepting up front that you will not be competing for the absolute top ranks unless willing to consider paying ridiculous amounts of money. The start is a bit faster if you give them a few euros/dollars and spend them wisely (buy some cards directly every day, not chests), which I think is fine, but after that there is not point in wasting money.
