A VPN is an excellent idea and should be taken seriously whenever you travel and use public WIFI. If you are using a MIFI hotspot I would be less concerned. Using public WIFI is very dangerous even when using SSL. I use a number consistently when doing Penetration Testing at work, so many exploits that can be leveraged and they are so easy to do on public internet. You can do a Man in the middle attack by pretending to be the campground WIFI. This will gain large amounts of data secure and non secure that can be either used to break into your banking or to harvest enough info to other sites to be able to build a profile to be able to guess common passwords, common "forgot password" answers etc. As part of a man in the middle attack, you can do deep packet inspection by providing the end user with a legitimate certificate (just not the one for the bank and they likely won't notice) to decrypt their data inline. There are many SSL flaws floating around right now, SHA1 has been end of life'd by all the Certificate authorities due to its insecurity and there are still a large majority of sites that have not yet upgraded to SHA2 because they are waiting for their current Cert to expire before doing it. This is just a small number of the many exploits that can be leveraged against you today with minimal skill, as so many exploits are already in hacker toolkits like the Metasploit Framework.
I would not rely on SSL alone, there are too many ways to compromise it.
I user CyberGhost. It has a free option as well as some premium options that are pricy. I managed to get a deal several times for about $20/year for a "basic premium" package. Their service has been rock solid. No need to worry about stability or security of "free" services. Remember free always costs someone, weather it is advertising, selling your surfing habits to third parties etc. Identity privacy is far more important that saving a few bucks on a free service. I would go with a service at a minimum offers both a free and paid option, their free option is far more likely to be trustworthy.
