Of course it's not cheating IM(most)HO.
99.9% of the spirit of peak bagging rules, both written and implied, is that you ascend to the summit and descend on your own power. (See
rules.) So you can't ride a dirt bike up. You can't take a ski lift down. Obvious no-nos.
Why would using a GPS as a navigational aid be cheating, but using a map or compass isn’t? I carry a GPS, but I don’t think I’ve ever used it to actually locate a summit. (Did I cheat?) Even if I did, I’d have no qualms about checking off that summit on my list.
If you really want to open up the discussion to different opinions, let’s ask if it’s cheating to use X/C skis to ascend or descend. How about butt sliding? Mountain bikes on logging roads? Using a sled in winter? Climbing ropes? Roller blading down MW Auto Rd.? I don't really want to ask these questions, only to point out that there are many gray areas.
In the end, it’s all in the head of the hiker. If you think using a GPS is cheating and I use one to navigate one of my hikes, I promise not to flash my patch at you (if and when I ever get one).
Rules or guidelines are there to set some standard. I may not agree with all of them, but there they are. Personally, I think I should get winter credit for hiking Liberty and Flume in April during a huge snow storm, but that guy over there shouldn’t because he did it on a warm, sunny day in January over bare ground. But I won’t and don’t really care. They’re just lists of mountains and sets of rules. I'll abide by them. What the heck.
I took a break last fall on the south ledges near the summit of Whiteface. Two climbers arrived after me and remarked that they thought this was the summit. I commented that the true summit was a little further along the trail in the woods. They casually responded that it was OK. This was a good enough summit for them. “Officially” they did not reach the summit, but in their minds, they did. Who really cares? (I didn’t report them and did not see anything in the news about a congressional investigation on the pair. And, yeah – I did take the extra 20 minutes to find the true summit, but that’s just me.)
So set your own standards where the rules are not specific and abide by them. Let the other guy do the same and let’s go hike.