The Philips Norelco One Blade Pro is a pretty good compact trimmer. It excels at it's primary job, namely cutting hair with an adjustable comb allowing you to go from a clean shave (sans comb) to a manicured trim. Battery life is excellent and it's safe travel feature, which prevents accidental turn-on during travel, ensures that you'll always have the full life available when you reach your destination. It has some of the same issues as other compact trimmers, namely that the comb can get choked with hair, so one needs to periodically clean that out if working with longer than about half an inch of hair growth. Where this really excels is in battery life, consistency of shave, post shave comfort, and consistent level adjustments with the comb.
The One Blade pro is a cordless rechargeable trimmer. It uses disposable trimming blades with a cost around $10 each. However, these blades will last significantly longer than a razor blade while providing just as clean a shave or the ability to trim hair to a custom height. The size and weight are pretty good for one-handed use and fully charged battery is good for weeks of use, assuming regular shaving. Build quality and design are pretty good - definitely stands out from cheap travel trimmers. It comes with a stand that while plastic, is weighted such that with the One Blade Pro attached, it does a good job at resisting tipping over from the random bumps that sometimes occur as you're moving around in front of the bathroom sink.
I'll admit, I also have the non-pro version of the One Blade. It comes with a set of fixed height combs. Like other compact trimmers, quality of height always seems to be an issue so I almost never bother with the combs. They either don't stay in place very well, the adjustment mechanism tends to be brittle, and I spend too much time manually correcting for height errors. That's not the case with the Pro. For those who work on manicuring beards or who may task their trimmers for light head duty, this is a significant improvement for trimmers in this class. Hands down, a winning feature.
Battery life is pretty good. However, good battery life is almost a requirement at this point. The One Blade Pro takes things a notch further by adding ON/OFF switch protection while traveling. By pressing the ON button for a few seconds, you activate a mode where a simple press will not cause the trimmer to turn ON. This is enough of an issue that I usually travel with either disposable razors or a cheap AAA battery powered trimmer where I can remove the battery. Even then, I tend to only use the razor or trimmer when absolutely necessary as they're typically a pain, too slow, and don't produce a quality shave. With the One Blade Pro, I can travel secure that my luggage won't start buzzing at random times, I'll have weeks of battery power left when I arrive at my destination with a quality trimmer. Even better, the One Blade Pro comes with a nice travel bag!
The trimmer does a good job with and without the comb. Sans comb, one can achieve a pretty close shave. A razor will still give a cleaner shave, so if you absolutely need the baby smooth skin that comes from a razor both removing hair and a layer of skin, this is not the trimmer for you. The ability of the comb to be consistent at achieving the set trim height is amazing. I tested this by shaving sections of my face at the 0.8, 2, and 4 levels. At first, I wasn't quite sure there was a difference between 0.8 and 2. Prepared for disappointment, I set the comb back to 0.8, and ran it over the 2mm shaved area. To my surprise, the hair there was visibly trimmed by half. The comb is pretty stable at longer hair lengths as well. While I'm hard pressed to think of a situation where I'd need that fine a granularity between "close shave" and "2mm stubble", it's goes to the quality of the design that I can achieve it.
In summary, I'm pretty impressed with the One Blade Pro. It's replacing my existing One Blade as my primary razor and will serve equally well as my travel razor. When this line was first introduced, I admit to thinking it was all hype. But now, after trying out the Pro, I'm a full convert.