Does iMessage work? What about texts? I’ve had the same number for years, can I keep it?
Yes, but as run no onna said. People iMessaging you will come through as normal. You iMessaging them will work as normal too BUT, instead of showing a phone number, it shows your email address or simply your name and image. People generally don't notice but sometimes they do. Anyone texting from any Mac, iPad or iPod Touch without an iPhone texts exactly the same way: email address used instead of phone.
Texts otherwise work fine. When I know or come to know I'm texting with an Apple person but not in iMessage, I simply switch to iMessage. When texting non-Apple people, I text using the VOIP app. Over the years, I've used Google Voice, Talkatone and Comcast Voice apps this way. All work fine for both voice and texting purposes. I really don't feel like I'm missing a thing.
911 service generally is NOT available, so that's a real tradeoff. However, I simply set up speed dialing for emergency services so I can select ONE "button" instead of having to hit three. Admittedly this is not as good as true 911. But I choose that seemingly modest tradeoff for the rest of the benefits.
A few related bonuses:
At home I still have land line phones and an alarm system and even a FAX machine to increasingly rarely need/use. There is a little box from Obihai that will link into Google Voice too. Landline connects to that box and the home phones, alarm and FAX machine use the same (or optionally a different) Google Voice number. Basically, at home, when someone calls my "cell," the Mini 6 rings along with my home phones. That all works perfectly fine and other than the one-time cost of that box, costs a whopping $0. Obihai has some add-on features for nominal amounts including a 911 service. I haven't added that but could.
Migrating my long-term phone number was easy, so that's now hosted at Google Voice and I could move it again if I ever wanted to change. I've also added a
second phone number at GV and have it forwarding to my main number. That second number can be texted or called and I readily use it for business.