I'm pleased with my Forerunner 45 (though see below), and with my pattern of use I haven't had any problems since the 3.10 firmware. But looking at the list of problems on this forum – including the post saying that GPS isn't working properly on a slew of devices – I'm honestly wondering whether Garmin has lost the plot. I've never seen so many complaints about a product, and it's no longer even a new product. Even given that some people here will simply have failed to RTFM – I've done that myself – there do seem to be a lot of problems.
The coaching facility on the Forerunner 45 is welcome and for me probably worth the upgrade.Apart from that I don't find it an improvement over the Forerunner 35. I only bought the 45 because the strap attachment lugs on the 35 broke after a couple of years. I don't think they were up to the job, and I hope the 45 lasts longer.