It's a multi-use thing for me: I hike and bike and generally bugger around. That means my GPS isn't handy, its safety kit*, and spare batteries go from nice to essential. All of which means I'll cheerfully hike on the moors in midwinter white-outs for a jolly (it really is liberating, having trustworthy kit: you can get lost and get home again, so I'm always bumbling off the track because hey, a pretty stone!).
That plus the sheer physical robustness of the Etrexes (sea kayaking with it
tied to the deck by string? How many times must I kill you, boy?) plus the low cost are all very attractive.
That they're hackable means it's happy nerds all round. The whole OpenStreetMap thing is a lovely piece of citizen nerdery that tickles my tickly bits; they work on most Garmins. They work trivially easily on Etrexes.
I won't upgrade until my current one gets eaten by a dinosaur, but I'm
definitely keeping an eye on the new models.
The specific training stuff, well, that's specific training stuff. My bike training is usually on the "miles / hours / pies" level of sophistication, so I'm not one to comment!
* Yes, yes, paper map and lodestone and powder of sympathy in a ziploc baggie too. Primary GPS user != dolt.
Reception during LEJOG has downgraded my trust in phone signal when I need it.