FYI - just did a quick search and actually the JBL Link 10 was £69 and the JBL Link 20 £89 at Curry's just a few days ago. Since they'll no doubt be this price again, I'd wait a get one of those.
Ha, good question. Tbh I've pretty much stopped looking at Bluetooth/smart speakers as I can't justify the expenditure, however it I was to get one now I'd be looking for one that had proper Google Home/Now/Assistant, Siri and/or Alexa integration. Just having a quick look, I think the most interesting ones available now look to be the JBL Link 10 or 20. These are still waterproof like this UE Boom but have plenty of the newer features this lacks. If you're less interested in the waterproof features then you've got loads of choices and top of my list to try would be the new Echo Plus. Obviously worth noting all of these are more than £75, but I'd be looking to pick one of them up when a bargain on one of them was available.
What do you consider a better buy?
"Siri and Google Now voice integration—just say it to play it" - don't you believe it! It worked for a bit but hasn't for a long time now. Not a bad price, but it's been cheaper and this a pretty old speaker now. A while ago I was going to get a second of these to pair up as well but things have just moved on so much I don't think this is a good buy anymore.