Loved the Giant Robo OVA, the two most memorable OVA's for me were Giant Robo and the original Area 88. Filler episodes often diminish a series's worth, perfect example was Kenshin, Shishio arc amazing, beg great, episodes between Shishio not too great, episodes after Shishio arc WTF.
PS Esteban if you are an anime fan Giant Robo is a must, if you have time (Nadia - 39 episodes) Naida is a classic that influenced many anime of today, particularly ones in the steampunk genre.