It's an okay wallet to have if you want a wallet that's accessible(mobile or desktop) so you don't have look for a new wallet whenever you plan on holding another altcoin but I wouldn't recommend it as a main wallet since it's risky to put everything you have in just one wallet. Also these past few days their tron wallet wasn't showing the balance correctly, the support was quick to reply(15-20mins) but the solutions he gave didn't help and other users experienced it as well.
yes, of course. I think is better have a little bit on exchange, a little bit on a specific wallet (example electrum) and a little bit on a wallet same Coinomi.The support is active answering any bad experience by users even here they also have representative here. 
I think he's one of their supports but it's best to join their telegram if you want a fast response from them. It is diversify the risk.