WordPress is extremely reliable, and far easier then maintaining a standard website.
For the first time these weekend I had an issue with it. I have a test site which is a duplicate of my main site, and whenever I upgrade a plug-in or WordPress itself, then I test first on my dev site.
I needed to update a plug-in on this site but WordPress got stuck in maintenance mode. A quick web search and I soon found the solution on WordPress’s support section. When the site goes into maintenance mode it creates a file in the root directory called “.maintenance”, this prevents the site being accessed or administrated, in order to login again you need to ftp into your site and delete this “.maintenance” file.
As with most things easy when you know how.