My Issues with WhatsApp:
NOTE: I only have the BB version so I don't know whats diff with the others.
1. Tied to my phone number.
I usually use these instant messengers as a way to vet people before I give them my actual phone number. I'll freely give out my BB Pin cuz I can easily delete and block you if I want. I'm very wary of giving out my "WhatsApp" because then they can call me whenever they want. Too personal too quick. Also means ppl who you might have given your number to for whatever reason a long time ago etc can now see ur profile pic/status etc and know when you're online etc. Sure you can block them but thats an 'opt out' system whereas BBM is 'opt in'. Also it makes people more wary of giving you their number for the same reason. However as stated before its a good way to get back in contacts u got out of touch with from before.
2. No message read indicator
Just message delivery. However the last seen indicator is nice.
3. No notifications
The BB version has no notifications for when people change their status or pictures. You actually have to look at each person in the list to see any difference. This has a profound effect on engagement. WhatsApp feels "boring" . When you have nothing to do you can always open up BBM and see what everyone's doing and comment on their status or pic and because of that people always come up with interesting or controversial updates because they know people will see them. Since WhatsApp is so passive people hardly change stuff because the hit rate is so low and gratification can be delayed. Make a change in BBM and a lot of ppl will notice within a few mins. Do it on WhatsApp and hours could pass before someone sees it and only because they were gonna talk to you anywayz. Don't underestimate the effect this has on engagement.
4. Slow
It might just be the BB version but loading stuff , esp the emoticons takes time where it becomes unresponsive.
5. Too many vague emoticons
Even if you restrict yourself to the People emoticons they're just too many of them that are only slightly different and there's no indicator of the use of each. At least with BBM the shortcuts act as descriptors for what the emoticons mean. They're also sufficiently different from each other so that each one fills a specific purpose. Yeah whatsapp has many many more but do u really want to spend the time searching through them to find the one that fits your mood precisely. Also your interpretation of what it means might differ from the recipient's just cuz they're so vague anywayz. Especially if u use a smaller font like me which has the sideeffect of squishing the emoticons up into indistinguishable blobs sometimes.
6. Remembers the last emoticon used.
At first glance this might seem like a good thing but you quickly realise its actually a hindrance. Sure sometimes you'll use the same emoticon over and over again but usually in MY conversations I'll use different ones. Since it remembers the last one used, every time u want to use a different emoticon from the last you have to spend time figuring out where the one you want is located relative to where you are now. That takes time and concentration ESPECIALLY since they're so many. With BBM, since it starts from the same place ALL the time, I know Wink is one swipe right, Devil is 2 swipes down and 2 swipes right etc. It becomes muscle memory and efficient.
I'm sure they're others but those are what I remember off the top of my head.