I've seen a few shaped handlegrips out there but never considered it myself. There must be some people here who've used them -- do they help? Are there any major drawbacks?

I replaced the stock grips with some Ergons. It did make a difference in comfort and helped with fatigue.

On a long ride, I have to change hand positions regularly. It sounds like those grips might be just the thing.

Basic Ergon Grip limits you to a single hand position, but it's more comfortable than with traditional grips. Ergon's are also available with built-in barends for multiple positions.

I used the original Ergon's on a flat bar hybrid and they helped improve comfort. But, nowhere near as comfortable as the recumbents I now ride ---> zero weight/pressure on arms and hands.

What do your handlebars look like?

There is no one universal ergonomic shape (for anything). If the hand grips that you are considering match the natural flow of your hands, wrists and forearms, you'll probably love them. If they don't you probably won't like them so much.

There is a big difference in the handlebar width and sweep back angle for straight handlebars and handlebars that have a rise. I doubt that an ergonomic hand grip shape that works ideally well for one will be comfortable on the other.

I use ergon shaped leather hand grips on the recumbent shown in my avatar and on my (straight handlebar) beater bike and I like them a lot. My son, on the other hand, tried some on his mountain bike which has a riser bar and hated them. Your mileage may vary.

My Krampus has a flat bar with a bit of upsweep. Hard part of this is that I haven't seen any at a local store, so all I can do is order a pair online and hope I like it. As long as they don't cost too much, that would be a reasonable option.

the bar end is integrated but adjustable separately

Ergon has a Cheaper Line _ Phorm .. that has a 1 piece short Bar end that is molded in,with the grip.. QBP stocks Both.

Ergons are really good grips. Another approach would be the Cane Creek Bar Stabilizers. The advantage there is an additional hand position, as the original grips are still there. There are a few other brands with a similar concept, but the Cane Creeks are worth the additional money.

My bike came with MTB flat bars and Ergons. I had problems with the bars so switched to a swept back style (on one Mary). I moved the Ergons and recently replaced them with the cork version.
Erons=good but won't make a wrong bar right